foo.cc: In function 'int main()':
foo.cc:12:9: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d%d",&n,&m);
    ~~~~~^~~~~~~~~~~~~~
foo.cc:13:26: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     for(i=0;i<n;i++)scanf("%d",&a[i]);
                     ~~~~~^~~~~~~~~~~~
foo.cc:14:25: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
    for(i=0;i<m;i++)scanf("%d",&b[i]);
                    ~~~~~^~~~~~~~~~~~